Process for the thermal cracking of hydrocarbons

ABSTRACT

A process for the thermal cracking of hydrocarbons by using a vertical cracking apparatus, comprising introducing raw hydrocarbon material containing components of low volatility or hydrocarbons of low volatility into a heat medium stream of heated steam of 1,600*-2,300*C, said introducing being in the form of a spray of liquid drops countercurrent to said heat medium steam and at an angle in the range of 120*-150*.

A nited States Patent Hosoi et a1.

[ Dec. 17, 1974 PROCESS FOR THE THERMAL CRACKING OF HYDROCARBONS Inventors: Takuji Hosoi, 4-513, Hyakunin-cho,

Shinjuku-ku, Tokyo; Masaaki Kanbayashi, 154-1, Harada, Nishiki-machi; Koichi Washimi, 1-6, Ochiai, Nishiki-machi, both of Iwaki-shi, Fukushima-ken; Shimpei Gomi, 1-6, Nakamura, Nerimaku, Tokyo, all of Japan Filed: Aug. 14, 1973 Appl. No.: 388,174

Related U.S. Application Data Continuation-impart of Ser. No. 163,420, July 16, 1971, abandoned, which is a continuation-in-part of Ser. No. 792,170, Jan. 17, 1969, abandoned.

Foreign Application Priority Data Jan. 25, 1968 Japan 434035 U.S. Cl. 260/683 R, 208/128, 208/130, 260/679 R Int. Cl. C07C 31/30 Field of Search 208/128, 130; 260/679 R, 260/683 R FEED [56] References Cited UNITED STATES PATENTS 2,942,043 6/1960 Rummert 260/679 3,242,224 3/1966 Howard 1 260/679 1,252,401 l/l9l8 Coast 208/128 2,904,502 9/1959 Shapleighm 260/683 2,111,899 3/1938 Nagel 260/683;

Primary Examiner-Delbert E. Gantz Assistant Examiner-C. E Spresser Attorney, Agent, or FirmLarson, Taylor and Hinds [57] ABSTRACT A process for the thermal cracking of hydrocarbons by using a vertical cracking apparatus, comprising introducing raw hydrocarbon material containing com ponents of low volatility or hydrocarbons of low volatility into a heat medium stream of heated steam of 1,6002,300C, said introducing being in the form of a spray of liquid drops countercurrent to said heat medium steam and at an angle in the range of 120150.

3 Claims, 2 Drawing Figures PATENTEDVDECI H974 3,. 855.339

FEED' FIG/ FEED I I [-76 TANGENT PROCESS FOR THE THERMAL CRACKING OF HYDROCARBONS This application is a continuation in part of our copending application, Ser. No. 163,420 filed on July 16, 1971, now abandoned, which is a continuation in part of our application, Ser. No. 792,170 filed on Jan. 17, 1969, already abandoned.

This invention relates to a process for the thermal cracking of hydrocarbons, more particularly a process for the thermal cracking of hydrocarbons containing components of low volatility such as, for example, crude oils and heavy fuel oils.

There have already been proposed many processes for producing useful gaseous unsaturated hydrocarbons such as acetylene, ethylene and propylene by thermally cracking at high temperatures easily volatile hydrocarbons such as methane and petroleum hydrocarbons. Among the processes for thermally cracking hydrocarbons containing high boiling fractions which cannot be volatilized even at 500C. under the normal pressure as, for example, crude oils and heavy fuel oils may be included a partial combustion system wherein oxygen is introduced directly into a liquid hydrocarbon oil and a sand cracker system wherein sand or coke is used as heat medium. However, the partial combustion system gives only a low yield of desired olefins and involves many other disadvantages such as troubles brought about by coke deposition in the reaction system due to unevenness of the temperature elevation on heating the raw materials, that is, non-uniformity of the cracking reaction. In the sand cracker system, on the other hand, the operation is very difficult and since the heat medium is solid, a comparatively long time is required to elevate the temperature for heating the feed material and hence no uniform thermal cracking can be achieved. Thus, the latter system further involves such disadvantages as a low yield of desired olefins and undesirable coke deposition due to excessive thermal cracking of a part of the product olefins.

As a result of elaborate investigations, we have now surprisingly found that if a raw hydrocarbon material of, or containing components of, low volatility is introduced into a vertical, cylindrical reactor in the form of a spray of liquid droplets in such a manner that the material is injected linearly in the radial direction toward the center axis of the reactor and in countercurrent at an angle of 120 to 150 to the passing direction of heat medium stream which is of high temperature steam, it is possible to effect instantaneous vaporization thermal cracking of even material or component of low volatility. In addition, due to such instantaneous vaporization in combination with the use of appropriate reaction conditions, i.e. temperature, pressure, time and others, even easily carbonizable components of low volatility can be thermally cracked substantially without being carbonized and thereby producing high yields of desired products. We have further found that if the inside wall of the reactor is heat-insulated or consciously maintained at a temperature of higher than 800C, preferably above 1000C by means of a heater and the like, the deposition of carbonaceous substances on the reactor wall can perfectly be prevented.

According to this invention, therefore, there is provided a process for the thermal cracking of hydrocarbons in a vertical, cylindrical cracking reactor comprising introducing a raw hydrocarbon material of, or containing components of, low volatility into the reactor in the form of a spray of liquid droplets in such a manner that the material is injected linearly in the radial direction toward the center axis of the reactor and in countercurrent at an angle of to 150 to the passing direction of heat medium stream which is of steam heated to a temperature of 1,600 2,300C.

According to a preferred embodiment of this invention, the cracking of the raw hydrocarbon material is effected at a temperature of 1,000 to 1,250C under a pressure of 0.3 to 6.0 kg/cm absolute for 0.002 to 0.01 seconds. The angle of is most preferred. According to a further preferred embodiment of this invention, the temperature of the inside wall of the reactor is consciously kept at a temperature of above 800C, and preferably above 1,000C so that the carbonization and deposition on the reactor wall of hardly volatile, high-boiling components in the raw hydrocarbon material and of tarry substances produced during the thermal cracking reaction can be prevented.

In the drawings attached, FIGS. 1 and 2 show the manner of injecting the raw hydrocarbon material into the reactor as specified above according to this invention. In FIG. 1 which is a rough, longitudinal section of a part of a vertical, cylindrical reactor at which the feed stream is introduced therein, a is the angle of 120 as specified above. FIG. 2 which is a rough cross section of the reactor of FIG. 1, shows that the feed stream is introduced linearly in the radial direction toward the center axis of the reactor.

The effect of using an angle ranging from 120 to 150 as defined above under the conditions specified above is very significant particularly with respect to the prevention of carbon deposition as compared with the use of angles outside the above range. Thus, if the angle is less than 120, no sufficient mixing of the raw material with the heat medium steam can be effected. On the other hand, if the angle is more than 150, smooth flowing of gases injected cannot be achieved. Therefore, a relatively long time is required for mixing the raw material with the heat medium steam, resulting in a considerable delay in the vaporization of components of low volatility in the raw material. In consequence, the thermal cracking reaction will undesirably be influ enced and further unvaporized liquid droplets will reach the wall of reactor to be carbonized and deposited on the wall with a very undesirable result. The relation between the angle for the injection and the amount of carbon deposit on the reactor wall will be explained in Example 4 hereinafter given.

The use as heat medium of steam heated to a temperature of 1,600 2,300C is essential according to this invention to heat the raw material instantaneously to a high temperature at which the components of low volatility in the raw material can instantaneously be vaporized.

As regards the temperature of the inside wall of the reactor, if the temperature drops below 800C, there is a tendency that tarry substances formed as by-products during the cracking condense on the wall and further it becomes difficult or impossible to remove carbon deposit from the wall by the fluid flowing along the wall On the other hand, if the temperature is maintained at a temperature above 800C, and preferably above 1,000C, the condensation of tarry substances on the wall can be avoided, or even if such condensation of tarry substances occurs, the contact of the condensed tarry substances with such high temperature wall causes an accelerated dehydrogenation of the tarry substances with the change in their structure and carbonaceous substances thus formed are much less adhesive in nature than the condensed tarry substances and easily removable from the wall if the speed of fluid flowing along the wall is sufficiently high.

The temperature of heat medium steam, the reaction temperature, pressure and time specified above are ptimum to produce desired unsaturated gaseous hydrocarbons such as acetylene, ethylene and propylene with the highest efficiency and to prevent coke and tar depositions.

Under these conditions, the process of this invention can solve many difficulties involved in the prior art and makes it possible to use as raw materials for industrial chemicals a variety of petroleum fractions which have been used only as fuels.

The method of the present invention shall be explained in detail in the following examples.

EXAMPLE 1 55 kg/hr. of steam at about 2,000C produced by a regenerative heating system were introduced into a vertical, cylindrical cracking reactor having an inside diameter of 30 mm. and a length of about 800 mm. lined with fire-bricks, and kg/hr. of a Khafji crude oil (percent recovered at 300C on atmospheric distillation: 45.3% by volume) preheated to about 350C were introduced linearly in the radial direction toward the center axis of reactor as fine droplets through spraying nozzles positioned at about 200 mm. below the inlet of the reactor. The angle a of the introduction of the raw material feed was 135 degrees countercurrent to the stream of the high temperature steam. The temperature of the inside wall in the lower half of the reactor was kept at about 1,050C by electric heating. The result obtained is shown in Table 1. Only a very small amount of g/m .hr. of carbonaceous substances was deposited on the inside wall of the reactor.

Further, on the thermal cracking reaction, a quencher was used to adjust the reaction time to 0.007 second. Then the reaction pressure was 0.7 kg/cm (gauge) and the final reaction temperature was about 1.120C.

TABLE 1 Gas composition Yield in "A by weight By way of comparison, the Khafji crude oil used above was thermally cracked under the same conditions in the same apparatus as in Example 1 except that the inside wall of the reactor was only heat-insulated without applying any positive heating. The result obtained is shown in Table 2. No difference was seen in the results of Tables 1 and 2, but 650 g./m .hr. of carbonaceous substances were deposited on the inside wall of the reactor. The temperature of the inside wall of the reactor was about 750C.

TABLE 2 Gas composition Yield in by weight Liquid composition Yield in by weight Benzene fraction Naphthalene do. Anthraccne do. Pitch Carbon black Unknown contents By way of further comparison, the same crude oil was introduced into the same reactor at the angle a of 45 to the stream of the high temperature steam, i.e. concurrently, under the same conditions as in Example 1. The result is shown in Table 3.

Since, in this case, the mixing was incomplete, not only the result was not good, out also carbonaceous substances were deposited in an amount of more than 1000 g/m .hr. over a length of about 30 mm. below the position at which the raw material was introduced, which thus made difficult a continuous operation for a long time.

TABLE 3 Gas composition Yield in "/1 by weight H 2.91 CPL 6.81 C H 18.52 C H 24.03 C -C 5.21 CO,CO- carbon 1.35

Liquid composition Yield in "/1 by weight Benzene fraction 7.89 Naphthalene do. 5.10 Anthraccne do. 6.00 Pitch 13.29 Carbon black 631 Unknown contents 2.58

EXAMPLE 2 Example 1 was repeated under the same conditions in the same apparatus as in Example 1 except that Seria Grude oil (APL, 37) was introduced in the form of a spray of fine droplets at the angle a of to the stream of high temperature steam. The results is shown in Table 4.

The result was satisfactory due to good mixing as similar as in Example 1. The quantity of carbon deposit on the inside wall of the reactor which was maintained at 1,000C. was as small as 24 g/m .hr.

TABLE 4 Gas composition Yield in "/1 by weight 11 2.80 Cl-L 6. 1 2 H, 20. 1 5

TABLE 4-Continued Gas composition Yield in by weight C l-l C6604 carbon) Liquid composition Yield in by weight stream of high temperature steam. The result is shown in Table 5.

The result was satisfactory due to good mixing as similar as in Example 1. The quantity of carbon deposit on the inside wall of the reactor which was maintained at 1,000C. was as small as 28 g/m .hr.

TABLE 5 Gas composition Yield in 70 by weight EXAMPLE 4 This example was given to illustrate the influence of the angle a on the tendency of carbon deposition on the inside wall of the reactor and on the time of continuous operation possible.

The method of Example 1 was repeated except that the angle a was varied over a range of 45 to 180. The amount of carbon deposit in g/cm .hr. and the time elapsed before the cracking operation was stopped due to troubles of the carbon deposition were recorded. The results are shown in Table 6.

TABLE 6 Angle (1 Amount of carbon Time of continuous (degrees) deposit (g/cm hr.) operation (hrs.)

Table 6 clearly shows that the use of angle 01 within the range of 120 to 150 according to this invention gave the best results which are unexpectedly significant over those outside the range.

What we claim is:

1. A process for the thermal cracking of hydrocarbons in a vertical, cylindrical cracking reactor comprising introducing a raw hydrocarbon material of, or containing components of, low volatility into the reactor in the form of a spray of liquid droplets in such a manner that the material is injected linearly in the radial direction toward the center axis of the reactor and countercurrent at an angle of 120 to 150 to the passing direction of heat medium stream which is of steam heated to a temperature of l,600 2,300C.

2. A process as claimed in claim 1 wherein the cracking temperature is 1,000 1,250C, the pressure is 0.3 6.0 kg/cm absolute, the time is 0.002 0.01 seconds, the angle is 135 and the temperature of the inside wall of reactor is more than 800C.

3. A process as claimed in claim 1 wherein the raw hydrocarbon material is selected from crude oils and 

1. A PROCESS FOR THE THERMAL CRACKING OF HYDROCARBONS IN A VERTICAL, CYLINDRICAL CRACKING REACTOR COMPRISING INTRODUCING A RAW HYDROCARBON MATERIAL OF, OR CONTAINING COMPONENTS OF, LOW VOLATILITY INTO THE REACTOR IN THE FORM OF A SPRAY OF LIQUID DROPLETS IN SUCH A MANNER THAT THE MATERIAL IS INJECTED LINEARLY IN THE RADICAL DIRECTION TOWARD THE CENTER AXIS OF THE REACTOR AND COUNTER-CURRENT AT AN ANGLE OF 120* TO 150* TO THE PASSING
 2. A process as claimed in claim 1 wherein the cracking temperature is 1,000* - 1,250*C, the pressure is 0.3 - 6.0 kg/cm2 absolute, the time is 0.002 - 0.01 seconds, the angle is 135* and the temperature of the inside wall of reactor is more than 800*C.
 3. A process as claimed in claim 1 wherein the raw hydrocarbon material is selected from crude oils and heavy fuel oils. 